Empirical equations for viscosity and specific heat capacity determination of fatty acids

Abstract

Phase change materials (PCM) used in thermal energy storage (TES) systems have been presented, over recent years, as one of the most effective options in energy storage. Saturated fatty acids are one of the most used PCM in TES systems, as they have high phase change enthalpy but in addition they do not present subcooling nor hysteresis and have proper cycling stability. The simulations and design of a TES system require the knowledge of the thermophysical properties of materials. Thermal conductivity, viscosity, specific heat capacity (Cp) can be experimentally determined, but these are material and time consuming tasks. To avoid or to reduce them, and to have reliable data without the need of experimentation, thermal properties can be determined by empirical equations. In this paper, three empirical equations are given to calculate the viscosity, solid Cp, and liquid Cp of the whole fatty acid family of PCM.

The work is partially funded by the Spanish government (ENE2015-64117-C5-1-R (MINECO/FEDER), ENE2015-64117-C5-2-R (MINECO/FEDER)). The authors would like to thank the Catalan Government for the quality accreditation given to their research group GREA (2014 SGR 123) and research group DIOPMA (2014 SGR 1543). The research leading to these results has received funding from the European Union’s Seventh Framework Programme (FP7/2007-2013) under grant agreement nº PIRSES-GA-2013-610692 (INNOSTORAGE) and from the European Union’s Horizon 2020 research and innovation programme under grant agreement nº 657466 (INPATH-TES). Dr. Camila Barreneche would like to thank Ministerio de Economia y Competitividad de España for Grant Juan de la Cierva, FJCI-2014-22886.